I tried to turn off the miners to see acitivty in MSI Afterburner for percentage of GPU used, and when I turned off miner on device 3, percentage use on gpu 2 went to 0. So i suspect it is not using the CPU, but the hashrate could lead you to believe it.

I will try guiminer now and post the results.

i decided to try poclbm to see which cores were available. I got this result:

Code:

PS C:\bitcoin\poclbm_py2exe_20101126> .\poclbm.exeNo device specified, you may use -d to specify ONLY ONE of the following

I will play some more and see if I can get a higher hash rate and make it run stable. Seems that perhaps the newest driver 11.5 have fixed some issues, because 11.4 would absolutely not work for me.

Yeah it's possible. I'm not using 11.4 either. I tried it on a recent miner and I had problems - driver crashes - so I went to 10.11.

Make sure you use the latest guiminer as it has support for the BFI_INT instruction. Another miner called Phoenix supports the same (it was the first to introduce it). Also keep an eye on a mining program called "hashkill"

I am running driver version 11.5 for the 5970 card (downloaded from ati page), and the ATI Stream SDK 2.4. I installed the driver first, then I installed the SDK after. I also went into ccc and unticked all boxes in the settings (sorry for the poor explanation, but I can't be bothered to fire up ccc again over the slow vnc connection to check which boxes I unticked.).

However I think it is the driver version and ATI Stream SDK version that fixed the problem. Once I saw that the GPU started working a little, I figured it was just a software problem. I thank everyone for trying to help me. And everything is now solved, alas nobody in particular helped me find the solution that worked, that I did find myself, so the bounty will be saved for now.

But if you are running a dual 5970 rig under windows 7, 64 bit, know it is possible to make it work, even without a crossfire cable. Hope this thread also helped somebody else but me!

Thanks again everybody, and have a great day! I am a happy man now!

allinvain: thanks for your suggestions, yes i do use phoenix as you see.